JP2009206880A - Lens array, read head and image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology with which difference in spots formed between lens columns can be suppressed and successful spots can be formed. <P>SOLUTION: A plurality of lens columns in which a plurality of lenses are arranged in the first direction are arranged in the second direction perpendicular or approximately perpendicular to the first direction, light can be made incident in the third direction, at least one lens surface of the lens has the free curved surface shape and has a plurality of focuses in the third direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lens array having a plurality of lenses, a reading head using the lens array, and an image reading apparatus.

  For example, an image reading apparatus described in Patent Document 1 is conventionally known as an apparatus that uses a technique for imaging light using a lens. In this apparatus, in addition to a reading head provided with a lens, an original table on which paper can be placed and a light source for irradiating light on the paper on the original table are arranged. As this type of image reading apparatus, there are an apparatus that detects reflected light reflected by a sheet and an apparatus that detects transmitted light that has passed through the sheet. In either apparatus, an image is formed using a lens. Light is detected. That is, in the apparatus that detects reflected light, the reflected light that is irradiated from the light source and reflected by the paper enters the reading head. On the other hand, in an apparatus that detects transmitted light, transmitted light that has been irradiated from a light source and transmitted through a sheet enters the reading head. The reading head includes a light receiving element in addition to the lens. Reflected light or transmitted light from the document table enters the lens and forms an image as a spot, and this spot is detected by the light receiving element. In this way, the reading head detects the reflected light or transmitted light from the paper, and the image on the paper can be read.

JP 2002-218167 A

  By the way, a lens array in which a plurality of lenses are arranged two-dimensionally can be used to cope with reading at a higher resolution. That is, in this lens array, a plurality of lens rows in which a plurality of lenses are arranged in the longitudinal direction are arranged in the width direction orthogonal or substantially orthogonal to the longitudinal direction. When reading is performed using this lens array, a plurality of light receiving elements (light receiving element groups) are arranged to face the lens in the traveling direction of light orthogonal or substantially orthogonal to the longitudinal direction and the width direction. Then, the reflected light or transmitted light from the mounting table (corresponding to the above document table) enters the lens from the traveling direction of the light and forms an image as a spot. And the spot formed in this way is detected by the light receiving element.

  However, an apparatus using a lens array in which a plurality of lenses are arranged two-dimensionally may cause the following problems. That is, there is a certain tolerance in the assembly accuracy of the reading head, the image reading apparatus, and the like. Therefore, there may be a case where a lens array mounting error occurs such that the lens array is tilted with respect to the mounting table. In such a case, there may be a difference in the distance (work distance) to the mounting table in the light traveling direction between the plurality of lens rows, and the spots formed between the plurality of lens rows may be different. . In addition, as a result of a difference in work distance between the plurality of lens rows due to vibration of the apparatus itself, there is a possibility that the spots differ between the plurality of lens rows. That is, due to such various causes, spots formed between the lens rows are different, and a good spot may not be formed.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique that can form a good spot by suppressing a difference in spots formed between lens rows.

  In order to achieve the above object, the lens array according to the present invention includes a plurality of lens rows in which a plurality of lenses are arranged in a first direction, and a plurality of lenses in a second direction orthogonal to or substantially orthogonal to the first direction. Light can enter in the third direction, and at least one lens surface of the lens has a free-form surface shape, and has a plurality of focal points in the third direction.

  In order to achieve the above object, a read head according to the present invention includes a head substrate having a light receiving element group in which a plurality of light receiving elements are grouped, and a lens array in which a lens is arranged facing the light receiving element group. In the lens array, a plurality of lens rows in which a plurality of lenses are arranged in the first direction are arranged in a second direction orthogonal or substantially orthogonal to the first direction, and the lenses face the light receiving element group in the third direction. At the same time, light incident from the opposite side of the light receiving element group in the third direction is emitted toward the light receiving element group, and at least one lens surface of the lens has a free-form surface shape, and a plurality of lenses are arranged in the third direction. It is characterized by having a focus.

  In order to achieve the above object, an image reading apparatus according to the present invention includes a head substrate having a light receiving element group in which a plurality of light receiving elements are grouped, and a lens array in which a lens is arranged facing the light receiving element group. In the lens array, a reading head in which a plurality of lens rows in which a plurality of lenses are arranged in the first direction is arranged in a second direction that is orthogonal to or substantially orthogonal to the first direction, and paper can be placed. A mounting table; and irradiation means for irradiating the mounting table with light. Reflected light that is irradiated from the irradiation unit and reflected by the sheet of the mounting table or transmitted light that has passed through the sheet is transmitted from the third direction to the lens. The reading head is arranged so as to be incident, the light receiving element group is opposed to the lens on the side opposite to the side where the reflected light or transmitted light in the third direction is incident, and the lens is reflected or transmitted. Toward the light receiving element group is injected, at least one lens surface of the lens has a free-form surface, it is characterized by having a plurality of focus in the third direction.

  In the invention thus configured (lens array, reading head, image reading apparatus), a plurality of lens rows in which a plurality of lenses are arranged in the first direction are arranged in a second direction orthogonal or substantially orthogonal to the first direction. Yes. The lens array is configured such that light can be incident on the lens in the third direction. When the light is imaged using the lens array, the light is incident on the lens in the third direction. However, when the lens array is used in this way, the spots formed between the plurality of lens rows differ due to the various causes described above, and the spots may not be formed satisfactorily. On the other hand, in the present invention, the lens surface of the lens has a free-form surface shape and has a plurality of focal points in the third direction. Therefore, for example, even when a lens array mounting error occurs, a difference in spot between lens rows is suppressed, and favorable spot formation is possible.

  Further, the lens array may be configured so that the respective focal points are arranged in a straight line or a substantially straight line in the third direction. With this configuration, it is possible to appropriately form spots.

  Further, the lens array may be configured so that each lens has the same configuration. This is because the configuration of the lens array can be simplified or the cost can be reduced.

  The lens may be formed of a photocurable resin. That is, the photocurable resin is cured by irradiating light. Therefore, since the lens array can be easily manufactured by forming the lens from the photocurable resin, the cost of the lens array can be suppressed.

  A lens may be formed on the glass substrate. That is, glass has a relatively small linear expansion coefficient. Therefore, by forming the lens on the glass substrate, it is possible to suppress the deformation of the lens array due to temperature change, and it is possible to realize good spot formation regardless of the temperature.

A. First Embodiment In the first embodiment, a case where a lens array according to the present invention is applied to a read head will be described. FIG. 1 is a perspective view showing an outline of a read head in the first embodiment. FIG. 2 is a partial cross-sectional view taken along line AA of the read head shown in FIG. 1, and is a cross section parallel to the optical axis of the lens. The AA line is the direction in which the lenses LS are arranged in a lens array LSC described later. In these figures, symbol LGD is the longitudinal direction of the read head 29, and symbol LTD is the width direction of the read head 29. The longitudinal direction LGD (first direction) and the width direction LTD (second direction) are orthogonal or substantially orthogonal to each other. The reading head 29 detects light incident from the object plane. In these figures, the reading head 29 is a direction from the object plane to the reading head 29 and is orthogonal or substantially orthogonal to the longitudinal direction LGD and the width direction LTD. Is shown as the traveling direction Doa (third direction) of the light beam. Moreover, the traveling direction Doa of the light beam is also shown as appropriate for the drawings used below. The traveling direction Doa of the light beam is parallel or substantially parallel to an optical axis OA described later.

  The reading head 29 includes a case 291, and positioning pins 2911 and screw insertion holes 2912 are provided at both ends in the longitudinal direction LGD of the case 291. When the reading head 29 is attached to an image reading apparatus or the like (not shown), the positioning pin 2911 is fitted into a positioning hole formed in the apparatus, and the reading head 29 is positioned in the apparatus. Further, the reading head 29 is positioned and fixed with respect to the apparatus by screwing and fixing the fixing screw into the screw hole of the apparatus through the screw insertion hole 2912.

  Inside the case 291, a head substrate 293, a light shielding member 297, and two lens arrays 299 (299A, 299B) are arranged. The inside of the case 291 is in contact with the front surface 293-h of the head substrate 293, while the back cover 2913 is in contact with the back surface 293-t of the head substrate 293. The back cover 2913 is pressed into the case 291 through the head substrate 293 by the fixing device 2914. That is, the fixing device 2914 has an elastic force that presses the back cover 2913 toward the inside of the case 291 (the upper side in FIG. 2), and the back cover is pressed by the elastic force, so that the inside of the case 291 is It is hermetically sealed (in other words, light does not leak from the inside of the case 291 and light does not enter from the outside of the case 291). A plurality of the fixing devices 2914 are provided in the longitudinal direction LGD of the case 291. A light receiving element group 295 in which a plurality of light receiving elements are grouped is provided on the surface 293-h of the head substrate 293.

  FIG. 3 is a plan view showing the configuration of the surface of the head substrate. FIG. 4 is a diagram showing a configuration of a light receiving element group provided on the head substrate surface. In FIG. 3, the lens LS is indicated by a broken line, but this is to show the correspondence between the lens LS and the light receiving element group 295, and does not indicate that the lens LS is provided on the head substrate surface. . As shown in FIG. 3, the light receiving element group 295 is configured by grouping eight light receiving elements 2951. The light receiving element 2951 is substantially square, and generates a current signal corresponding to the amount of received light. In each light receiving element group 295, these light receiving elements 2951 are arranged as follows. That is, as shown in FIG. 4, in the light receiving element group 295, four light receiving elements 2951 are arranged along the longitudinal direction LGD to form a light receiving element row 2951R, and two light receiving element rows 2951R are arranged in the width direction LTD. Are arranged side by side with the light receiving element row pitch Pelr. The respective light receiving element rows 2951R are shifted from each other by the element pitch Pel in the longitudinal direction LGD, and the positions of the respective light receiving elements 2951 in the longitudinal direction LGD are different from each other. The light receiving element group 295 configured as described above has a longitudinal width Wegg in the longitudinal direction LGD and a width in the width direction LTD, and the longitudinal width Wegg is longer than the width in the width Wegt. .

  On the surface 293-h of the head substrate 293, a plurality of light receiving element groups 295 configured in this way are arranged. That is, three light receiving element groups 295 are arranged at positions different from each other in the width direction LTD to form a light receiving element group column 295C, and a plurality of light receiving element group columns 295C are arranged along the longitudinal direction LGD. In each light receiving element group column 295C, the three light receiving element groups 295 are shifted from each other by the light receiving element group pitch Peg in the longitudinal direction LGD. As a result, the position PTE in the longitudinal direction LGD of each light receiving element group 295 is Different from each other. In other words, on the surface 293-h of the head substrate 293, a plurality of light receiving element groups 295 are arranged in the longitudinal direction LGD to form a light receiving element group row 295R, and three light receiving element group rows 295R are arranged in the width direction LTD. The light receiving element groups are arranged at a row pitch Pegr. The respective light receiving element group rows 295R are arranged to be shifted from each other by the light receiving element group pitch Peg in the longitudinal direction LGD. As a result, the positions PTE in the longitudinal direction LGD of the respective light receiving element groups 295 are different from each other.

  Thus, the plurality of light receiving element groups 295 are two-dimensionally arranged on the head substrate 293. In the figure, the position of the light receiving element group 295 is represented by the center of gravity position of the light receiving element group 295, and the position PTE in the longitudinal direction LGD of the light receiving element group 295 is the longitudinal axis from the position of the light receiving element group 295. It is represented by a vertical leg down to LGD.

  As will be described later, in the lens array 299 (299A, 299B), a lens LS is arranged for each light receiving element group 295. That is, the light receiving element group 295 and the lens LS are arranged in a one-to-one correspondence. A light shielding member 297 is provided between the lens array 299A of the two lens arrays 299 and the head substrate 293.

  Referring again to FIGS. 1 and 2, a light shielding member 297 is disposed in contact with the surface 293-h of the head substrate 293. A light guide hole 2971 is formed in the light shielding member 297. Specifically, the light guide holes 2971 are formed so as to communicate between the lenses LS and the light receiving element groups 295 arranged in correspondence with each other, and each light guide hole 2971 is a traveling direction of the light beam. It is formed to penetrate Doa. Accordingly, the light beam emitted from the lens LS of the lens array 299A passes through the light guide hole 2971 and travels toward the corresponding light receiving element group 295. Since such a light shielding member 297 is provided, a light beam from the lens LS provided correspondingly efficiently enters the light receiving element group 295, while an unnecessary light beam enters the light receiving element group 295. Is suppressed.

  FIG. 5 is a plan view of the lens array in the first embodiment, and corresponds to a case where the lens array is viewed from the object plane side. In addition, each lens LS in the same figure is formed in the back surface 2991-t of the lens array board | substrate 2991, and the same figure has shown the structure of this lens array board | substrate back surface 2991-t. In the lens array 299, a lens LS is provided for each light receiving element group 295. That is, in the lens array 299, the lens array LSC is configured by arranging three lenses LS arranged at different positions in the width direction LTD, and a plurality of lens arrays LSC are arranged along the longitudinal direction LGD. . In each lens row LSC, three lenses are arranged so as to be shifted from each other by a lens pitch Pls in the longitudinal direction LGD. As a result, the positions PTL of the lenses LS in the longitudinal direction LGD are different from each other.

  In other words, in the lens array 299, a plurality of lenses LS are arranged in the longitudinal direction LGD to form a lens row LSR, and three lens rows LSR are provided at the lens row pitch Plsr in the width direction LTD. The lens rows LSR are arranged so as to be shifted from each other by the lens pitch Pls in the longitudinal direction LGD, and the positions PTL of the lenses LS in the longitudinal direction LGD are different from each other. Thus, in the lens array 299, the plurality of lenses LS are two-dimensionally arranged. In the figure, the position of the lens LS is represented by the apex of the lens LS (that is, the point where the sag is maximum), and the position PTL in the longitudinal direction LGD of the lens LS is long from the apex of the lens LS. It is represented by a leg with a perpendicular line down to the direction axis LGD.

  FIG. 6 is a longitudinal sectional view of the lens array, the head substrate, etc., and shows a longitudinal sectional view including the optical axis of the lens LS formed in the lens array. The lens array 299 has a lens array substrate 2991 that is long in the longitudinal direction LGD and is light transmissive. In the first embodiment, the lens array substrate 2991 is formed of glass having a relatively small linear expansion coefficient. Of the front surface 2991-h and the back surface 2991-t of the lens array substrate 2991, a lens LS is formed on the back surface 2991-t of the lens array substrate 2991. The lens array 299 is formed by a method described in, for example, Japanese Patent Application Laid-Open No. 2005-276849. That is, a mold having a concave portion corresponding to the shape of the lens LS is brought into contact with a glass substrate as the lens array substrate 2991. A photocurable resin is filled between the mold and the light transmissive substrate. When this photocurable resin is irradiated with light, the photocurable resin is cured and a lens LS is formed on the light transmissive substrate. Then, when the photocurable resin is cured and the lens LS is formed, the mold is released. Each lens LS formed in the lens array 299 has the same configuration.

  Thus, in the first embodiment, the lens array 299 is configured by the lens array substrate 2991 and the lens LS. Therefore, the degree of freedom of the configuration of the lens array 299 is improved, for example, it is possible to select different base materials for the lens array substrate 2991 and the lens LS. Therefore, the lens array 299 can be appropriately designed according to the specifications required for the reading head 29, and good exposure by the reading head 29 can be more easily realized. In the first embodiment, the lens LS is formed of a photocurable resin that can be quickly cured by irradiation with light. Therefore, since the lens LS can be easily formed, the manufacturing process of the lens array 299 is simplified, and the cost of the lens array 299 can be reduced. Further, since the lens array substrate 2991 is made of glass having a small linear expansion coefficient, deformation of the lens array 299 due to temperature change is suppressed, and good exposure can be realized regardless of temperature.

  In the reading head 29, the lens array 299 having such a configuration is arranged side by side in the traveling direction Doa of two (299A, 299B) light beams. These two lens arrays 299A and 299B are opposed to each other with a pedestal 296 interposed therebetween, and the pedestal 296 functions to define the interval between the lens arrays 299A and 299B. As described above, in the first embodiment, the two lenses LS1 and LS2 arranged in the light beam traveling direction Doa are arranged for each light receiving element group 295 (FIGS. 1, 2, and 6). Also, the optical axis OA (the two-dot chain line in FIG. 6) passing through the center of each of the first lens LS1 and the second lens LS2 corresponding to the same light receiving element group 295 is orthogonal to or substantially the back surface 293-t of the head substrate 293. Orthogonal. Here, the lens LS of the lens array 299A downstream of the light beam traveling direction Doa is the first lens LS1, and the lens LS of the lens array 299B upstream of the light beam traveling direction Doa is the second lens LS2. . In other words, the light beam from the object surface enters the second lens LS2, and then enters the first lens LS1. Thus, in the first embodiment, since the plurality of lens arrays 299 are arranged in the light beam traveling direction Doa, the degree of freedom in optical design can be improved.

  As described above, the reading head 29 includes the imaging optical system having the first and second lenses LS1 and LS2. The imaging optical system is opposed to the object plane in the light beam traveling direction Doa (in other words, the opposing direction of the imaging optical system and the object plane), and each lens LS is separated from the object plane. A light beam is incident. Therefore, the light beam incident from the object plane is imaged by the first and second lenses LS1, LS2, and a spot SP is formed on the head substrate surface 293-h. In the first embodiment, the second lens LS2 is a single focus lens having a single focal point, while the first lens LS is a multifocal lens having a plurality of focal points. That is, the lens surface LSF of the first lens LS has a plurality of regions LR, and the positions of the focal points FP of the plurality of regions LR are different from each other in the light beam traveling direction Doa (third direction). Yes.

  FIG. 7 is a diagram showing the configuration of the first lens, and the “sectional view” column in the upper part of FIG. 7 corresponds to the sectional view of the first lens LS including the optical axis OA, and the “plan view” in the lower part of FIG. The column corresponds to a plan view when the first lens is viewed from the downstream side (light receiving element group side) of the light beam traveling direction Doa. The lens surface LSF of the first lens LS1 has a free-form surface shape, and the lens surface LSF has a plurality of focal points FP in the light beam traveling direction Doa. Specifically, it is as follows. As shown in FIG. 7, the first lens LS1 has a rotationally symmetric shape with respect to the optical axis OA. The lens surface LSF of the first lens LS is divided into three regions LR. That is, the first region LR1 located in the center, the second region LR2 located outside the first region LR1, and the third region LR3 located further outside the first and second regions LR1 and LR2 are provided. Are provided on the lens surface LSF. The first region LR1 is a circular region centered on the optical axis OA. The second region LR2 is an annular region (ring-shaped region) that surrounds the first region LR1 and is concentric with the first region LR1. Further, the third region LR3 is an annular region (ring-shaped region) that surrounds the first and second regions LR1 and LR2 and is concentric with the first region LR1 (and the second region LR2). As shown in the “Cross sectional view” column of the same figure, the lens has a thicker lens thickness in the order of the first region LR1, the second region LR2, and the third region LR. That is, the first region LR1 has the thickest lens thickness, and the third region LR3 has the thinnest lens thickness. The regions LR1 to LR3 have different focal points FP.

  FIG. 8 is a diagram showing the position of the focal point of the first lens, and shows a case where parallel light is incident on the first lens LS1 from the image plane side (that is, the light receiving element group side). As shown in the figure, the light beams LB before entering the first lens LS1 are parallel to each other. However, the trajectory of the light beam LB after entering the first lens LS1 differs depending on which region LR of the lens surface LSF the light beam LB has entered. That is, the first light beam LB1 incident on the first region LR1 is imaged at the focal point FP1 of the first region LR1, and the second light beam LB2 incident on the second region LR2 is focused on the focal point FP2 of the second region LR2. The third light beam LB3 that has been imaged and entered the third region LR3 is imaged at the focal point FP3 of the third region LR3. The positions of the focal points FP1 to FP3 are different from each other in the traveling direction Doa of the light beam, and are arranged linearly or substantially linearly in the traveling direction Doa of the light beam in the order of the focal point FP3, the focal point FP1, and the focal point FP2. .

  Thus, the first lens LS1 functions as a multifocal lens having a plurality of focal points FP1 to FP3. Therefore, even if the position of the object point VOP (FIG. 6) is slightly deviated in the light beam traveling direction Doa, the shape and size of the spot SP formed on the head substrate surface 293-h does not vary so much and is substantially constant. It becomes. Therefore, for example, even when an attachment error of the lens array 299 occurs, a difference in spot between the lens rows LSR is suppressed, and a favorable spot formation is possible.

  That is, the light beam emitted from a certain object point VOP passes through the multifocal lens LS1, and is thus imaged at each of a plurality of imaging positions arranged in the traveling direction Doa of the light beam. In other words, a plurality of imaging light beams are arranged in the light beam traveling direction Doa. Therefore, even if the position of the object point VOP shifts in the light beam traveling direction Doa, the imaging light beam on the head substrate surface 293-h or the head substrate surface 293-h among the plurality of imaging light beams. The spot SP is favorably formed by the near imaging light beam. Therefore, the spot SP formed on the head substrate surface 293-h has a substantially constant shape and size regardless of the fluctuation of the object point VOP.

  In order to describe the case where the object point VOP is specifically deviated, the light beam emitted from each of the object points VOP1 to VOP3 is spotted on the head substrate surface 293-h using FIG. A mode that SP is formed is shown. In the figure, the object point VOP1 corresponds to the case where there is no position shift, and the object points VOP2 and VOP3 correspond to the case where the position shift occurs upstream and downstream in the light beam traveling direction Doa, respectively. Of the light beam emitted from the object point VOP1, the light beam that has passed through the region LR1 of the first lens LS1 is imaged as a spot SP on the head substrate surface 293-h. Further, among the light beams emitted from the object point VOP2, the light beam that has passed through the region LR2 of the first lens LS1 is imaged as a spot SP on the head substrate surface 293-h. Further, among the light beams emitted from the object point VOP3, the light beam that has passed through the region LR3 of the first lens LS1 is imaged as a spot SP on the head substrate surface 293-h. Thus, in the first embodiment, any of the object points VOP1 to VOP3 at different positions can form a substantially constant spot SP on the head substrate surface 293-h. That is, even if the position of the object point VOP is shifted, the spot SP formed on the head substrate surface 293-h can be made substantially constant.

  Thus, in the lens array 299A according to the first embodiment, a plurality of lens rows LSR in which a plurality of lenses LS are arranged in the longitudinal direction LGD are arranged in the width direction LTD. Light can enter each lens LS in the light beam traveling direction Doa. Moreover, the lens surface LSF of the lens LS has a free-form surface shape, and has a plurality of focal points FP in the light beam traveling direction Doa. Therefore, even if the distance from the object plane (work distance) differs for each lens row LSR, the formed spot SP is substantially constant. Therefore, it is possible to form a good spot SP.

  In the first embodiment, since the plurality of focal points FP1 to FP3 of the first lens LS1 are arranged linearly or substantially linearly in the light beam traveling direction Doa, a better spot SP can be formed. It becomes possible. This will be described. When the focal points FP1 to FP3 are not arranged linearly or substantially linearly in the traveling direction Doa but arranged in a zigzag manner, a plurality of imaging positions where the light beam is imaged are also arranged in a zigzag manner. Become. Therefore, when the position of the object point VOP changes in the traveling direction Doa of the light beam, the position of the spot SP formed on the head substrate surface 293-h is a direction orthogonal or substantially orthogonal to the traveling direction Doa of the light beam (that is, There is a possibility of fluctuation in the plane of the head substrate surface 293-h). As a result, a light receiving element 2951 different from the light receiving element 2951 that should originally detect the spot may detect the spot SP, and an error may occur in the reading operation. On the other hand, in the first embodiment, the plurality of focal points FP1 to FP3 are linearly or substantially linearly arranged in the traveling direction Doa of the light beam, so that the imaging position is also linear in the traveling direction Doa of the light beam. Or it is arranged in a substantially straight line. As a result, the spot SP is formed at an appropriate position, and the occurrence of an error in the reading operation is suppressed.

  In the first embodiment, one of the plurality of regions LR (first region LR1) is a circular region, and other regions (second region LR2, third region LR3) other than the one region. Is a ring-shaped region surrounding the circular region and concentric with the circular region. Therefore, the shape of the lens surface LSF of the first lens LS1 is a rotationally symmetric shape centered on the concentricity of the circular region and the ring-shaped region. Therefore, the lens LS1 can be easily configured, and the configuration of the lens array 299A is simplified or reduced in cost.

  In the first embodiment, the lens array 299A is configured so that the lenses LS of the lens array 299A have the same configuration. That is, the configuration of the lens array 299 can be simplified or reduced in cost, which is preferable.

B. Second Embodiment In the second embodiment, a case where the reading head 29 in the first embodiment is applied to an image reading apparatus will be described. FIG. 9 is a plan view schematically illustrating an image reading apparatus equipped with the reading head according to the first embodiment. A document table 11 is provided above the main body 10 of the image reading apparatus 1. The surface of the document table 11 is configured such that the document 2 as a sheet can be placed. When the image of the document 2 is read, the document 2 is placed on the surface of the document table 11 by the user. A document guide 12 for restricting the movement of the document 2 and positioning the document 2 is provided around the document table 11. A white reference member 13 is provided on one side of the document guide 12 so as to face the document table 11, and this white reference member 13 is used when reading a white reference at the time of so-called shading correction.

  A carriage 22 that is movable in a sub-scanning direction SD that is orthogonal or substantially orthogonal to the main scanning direction MD is disposed below the document table 11. A light source 21 and a read head 29 are arranged on the carriage 22. The reading head 29 is held such that its longitudinal direction LGD is parallel or substantially parallel to the main scanning direction MD, and its width direction LTD is parallel or substantially parallel to the sub-scanning direction SD. The reading head 29 has the lens array 299 facing the document table 11, and the reflected light from the document 2 on the document table 11 enters the reading head 29 from the traveling direction Doa of the light beam through the lens arrays 299 B and 299 A. Incident. The light receiving element group 295 is disposed opposite to the lenses LS1 and LS2 on the side opposite to the side where the reflected light is incident in the light beam traveling direction Doa. Accordingly, the reflected light is imaged as a spot SP by the lenses LS 1 and LS 2 and detected by the light receiving element 2951.

  The light source 21 includes three types of LEDs (Light Emitting Diodes) corresponding to red, green, and blue colors. A plurality of LEDs of each color are arranged in the main scanning direction MD. When the light source 21 emits light, the reflected light from the document 2 enters the reading head 29. As described above, the light beam incident on the reading head 29 is detected by the light receiving element 2951 and converted into a current signal. Further, the carriage 22 is provided with an A / D converter 24. The A / D converter 24 converts an analog current signal output from the light receiving element 2951 into a digital signal. The carriage 20 moves upon receiving a driving force from the driving unit 30. The driving means 30 uses a stepping motor (not shown) to move the carriage 20 in the sub scanning direction SD at a constant speed.

  Inside the main body 10, a CPU (Central Processing Unit) 41, a data creation unit 42, a RAM (Random Access Memory) 43, and a ROM (Read Only Memory) 44 are provided. The CPU 41 functions as a controller that controls the entire image reading apparatus 1, and performs processing of the moving speed of the carriage 20, the light amount of the light source 21, image data created by the data creation unit 42, and the like. The RAM 43 temporarily stores digital data created from the digital signal output from the A / D converter 24, image data created by the data creation unit 42 based on the digital data, and the like. The ROM 44 stores a program for the CPU 41 to control each part of the image reading apparatus 1.

  FIG. 10 is a diagram illustrating an image reading operation in the image reading apparatus. In the image reading operation, each pixel PX of the document image is sequentially read while moving the reading head 29 in the sub scanning direction SD. The drawing shows the reading order of each pixel PX on the original image. The hatched pixel PX in FIG. 1 indicates the pixel read by the first reading operation, and the second time in FIG. The hatched pixel PX indicates a pixel that is read by the second reading operation, and the third hatched pixel PX indicates a pixel that is read by the third reading operation. As described in detail in the first embodiment, in the reading head 29, the light receiving element groups 295 are two-dimensionally arranged. Therefore, for example, the reading operation described in Patent Document 1 that sequentially reads pixels for one line arranged in the main scanning direction MD is different from the reading operation of this embodiment.

  In the first reading operation, a document image is read for each pixel group PXG composed of eight pixels PX. Here, the pixel group PXG_1 is a pixel group read by the light receiving element group 295_1. Similarly, the pixel groups PXG_2 to PXG_4 are pixel groups read by the light receiving element groups 295_2 to PXG_4. In the second reading operation, the pixel group PXG (the second hatching pixel group) located downstream by one pixel in the sub-scanning direction SD from the pixel group PXG read the first time is read. Furthermore, in the third reading operation, a pixel group PXG (a pixel group for the third hatching pattern) located downstream by one pixel in the sub-scanning direction SD from the pixel group PXG read the second time is read. In this way, the reading operation is sequentially performed, so that the pixels PX of the entire document image can be read. In the color image reading operation, each color LED of the light source 21 is individually turned on to obtain pixel data for each color.

  As described above, the image reading apparatus according to the second embodiment includes the reading head 29 described in detail in the first embodiment. Therefore, even if the distance (work distance) from the surface of the document table 11 differs for each lens row LSR, the formed spot SP is substantially constant. Therefore, it is possible to form a favorable spot SP, and it is possible to execute an image reading operation with high accuracy.

C. Others As described above, in the above embodiment, the lens array 299A corresponds to the “lens array” of the present invention, and the first lens LS1 corresponds to the “lens” of the present invention. The longitudinal direction LGD and the main scanning direction MD correspond to the “first direction” of the present invention, the width direction LTD and the sub-scanning direction SD correspond to the “second direction” of the present invention, and the light beam traveling direction Doa Corresponds to the “third direction” of the present invention. The document table 11 corresponds to the “mounting table” of the present invention, and the light source 21 corresponds to the “irradiating means” of the present invention.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the above embodiment, the number of light receiving elements 2951 aligned in the longitudinal direction LGD in the light receiving element row 2951R is four, and the number of light receiving element rows 2951R aligned in the width direction LTD in the light receiving element group 295 is two. However, the number of the light receiving elements 2951 constituting the light receiving element row 2951R and the number of the light receiving element rows 2951R constituting the light receiving element group 295 are not limited thereto. Therefore, the light receiving element group 295 can be configured as shown below.

  FIG. 11 is a plan view showing another configuration of the light receiving element group. FIG. 12 is a diagram showing the configuration of the back surface of the head substrate in which a plurality of light receiving element groups of FIG. In another configuration shown in FIG. 11, 15 light receiving elements 2951 are arranged in the longitudinal direction LGD to form a light receiving element row 2951R. In the light receiving element row 2951R, the light receiving elements 2951 are arranged at a pitch (= 0.084 [mm]) four times the element pitch Pel (= 0.021 [mm]). The four light receiving element rows 2951R thus configured are arranged in the width direction LTD (2951R-1, 2951R-2, 2951R-3, 2951R-4). In the width direction LTD, the pitch between the light receiving element row 2951R-4 and the light receiving element row 2951R-1 is 0.1155 [mm], and between the light receiving element row 2951R-4 and the light receiving element row 2951R-2. The pitch is 0.084 [mm], and the pitch between the light receiving element row 2951R-4 and the light receiving element row 2951R-3 is 0.0315 [mm]. When a straight line that passes through the center (center of gravity) of the light receiving element group 295 and is parallel to the width direction LTD is a center line CTL, each of the light receiving element row 2951R-1 and the light receiving element row 2951R-4 and the center line CTL The pitch is 0.05775 [mm].

  In FIG. 11, two rows 2951R-1 and 2951R-2 above the center line CTL constitute one light receiving element row set 2951RT, and two rows 2951R-3 and 2951R- below the center line CTL. 4 constitutes one light receiving element row set 2951RT. In each light receiving element row set 2951RT, the two light receiving element rows 2951R are shifted from each other by twice the element pitch Pel (= 0.021 [mm]) in the longitudinal direction LGD (= 0.042 [mm]). Moreover, the two light receiving element row groups 2951RT are shifted from each other by the element pitch Pel (= 0.021 [mm]) in the longitudinal direction LGD. Accordingly, the four light receiving element rows 2951R are shifted from each other by the element pitch Pel (= 0.021 [mm]) in the longitudinal direction LGD. As a result, the positions of the respective light receiving elements 2951 in the longitudinal direction LGD are different. Yes. Here, when the light receiving elements 2951 located at both ends in the longitudinal direction LGD of the light receiving element group 295 are end light receiving elements 2951x, the pitch between the end light receiving elements 2951x in the longitudinal direction LGD is 1.239 [mm] The pitch between the end light receiving element 2951x and the center of the light receiving element group 295 in the longitudinal direction LGD is 0.6195 [mm].

  In the example shown in FIG. 12, the light receiving element groups 295 shown in FIG. 11 are two-dimensionally arranged. As shown in FIG. 12, a plurality of light receiving element groups 295 are arranged in the longitudinal direction LGD to form a light receiving element group row 295R. In the light receiving element group row 295R, the light receiving element groups 295 are arranged at a pitch (= 1.778 [mm]) three times the light receiving element group pitch Peg. The three light receiving element group rows 295R (295R-1, 295R-2, 295R-3) configured as described above are arranged in the width direction LTD with the light receiving element group row pitch Pegr (= 1.77 [mm]). Are lined up. The light receiving element group rows 295R are shifted from each other by the light receiving element group pitch Peg (about 0.593 [mm]) in the longitudinal direction LGD. That is, the light receiving element group row 295R-1 and the light receiving element group row 295R-2 are shifted by 0.59275 [mm] in the longitudinal direction LGD, and the light receiving element group row 295R-2 and the light receiving element group row 295R-3 Is shifted by 0.5925 [mm] in the longitudinal direction LGD, and the light receiving element group row 295R-3 and the light receiving element group row 295R-1 are shifted by 0.59275 [mm] in the longitudinal direction LGD. . Therefore, the light receiving element group row 295R-1 and the light receiving element group row 295R-3 are shifted by 1.18525 [mm] in the longitudinal direction LGD.

  In the above embodiment, the case where the lens array 299A according to the present invention is applied to the read head 29 has been described. However, the application target of the lens array 299A is not limited to the read head 29.

  In the image reading apparatus according to the second embodiment, the reading head 29 detects the reflected light from the document 2. However, the configuration can be modified as follows. That is, the light source 2 and the reading head 29 sandwich the original table 11 so that the light source 2 is disposed opposite to the reading head 29 and the reading head 29 can detect the transmitted light transmitted through the original 2. .

  In the embodiment described above, three lens rows LSR are arranged in the width direction LTD. However, the number of lens rows LSR is not limited to three, and the present invention can be applied to a configuration having two or more lens rows LSR.

  In the above embodiment, the multifocal lens LS1 is configured by forming the lens LS on the back surface 2991-t of the lens array substrate. However, the lens array 299A may be configured by forming the multifocal lens LS1 on the surface 2991-h of the lens array substrate 2991.

  In the above embodiment, among the plurality of lenses LS constituting the imaging optical system, the first lens LS1 is configured as a multifocal lens, but the second lens LS2 may be configured as a multifocal lens. .

  In the above embodiment, the multifocal lens LS1 has three focal points. However, the number of focal points of the multifocal lens LS1 is not limited to three, and may be two or more.

  In the above embodiment, the first lens LS1 has a rotationally symmetric shape with respect to the optical axis OA. However, it is not an essential requirement for the present invention that the shape of the first lens LS1 is rotationally symmetric with respect to the optical axis OA.

  In the above embodiment, two lens arrays 299 are used, but the number of lens arrays 299 is not limited to this.

  In the above embodiment, the lens array 299 is configured by forming the lens LS on the lens array substrate 2991. That is, the lens array substrate 2991 and the lens LS are configured separately. However, the lens array substrate 2991 and the lens LS can be integrally formed of the same material.

  In the above embodiment, the lenses LS1 of the lens array 299A have the same configuration. However, it is not essential for the present invention that these lenses LS1 have the same configuration. Therefore, the lens LS1 can be configured to have a different configuration.

FIG. 3 is a perspective view illustrating an outline of a reading head in the first embodiment. FIG. 2 is a partial cross-sectional view taken along line AA of the read head illustrated in FIG. 1. The top view which shows the structure of the surface of a head board | substrate. The figure which shows the structure of the light receiving element group provided in the head substrate surface. The top view of the lens array in 1st Embodiment. Sectional drawing of a longitudinal direction, such as a lens array and a head board | substrate. The figure which shows the structure of a 1st lens. The figure which shows the position of the focus of a 1st lens. FIG. 2 is a plan view schematically showing an image reading apparatus equipped with the reading head according to the first embodiment. FIG. 6 is a diagram illustrating an image reading operation in the image reading apparatus. The top view which shows another structure of a light receiving element group. The figure which shows the structure of the back surface of the head board | substrate which arranged multiple light receiving element groups of FIG.

Explanation of symbols

  29 ... Reading head, 293 ... Head substrate, 295 ... Light receiving element group, 2951 ... Light receiving element, 299, 299A, 299B ... Lens array, 2991 ... Lens array substrate, LS, LS1, LS2 ... Lens, LR, LR1, LR2, LR3 ... area, FP, FP1, FP2, FP3 ... focus, SP ... spot, MD ... main scanning direction (first direction), SD ... sub-scanning direction (second direction), LGD ... longitudinal direction (first direction), LTD: width direction (second direction), Doa: light beam traveling direction (third direction), 11: document table (mounting table), 21: light source (irradiation means)

Claims (7)

  A plurality of lens rows in which a plurality of lenses are arranged in a first direction are arranged in a second direction that is orthogonal or substantially orthogonal to the first direction, and the lens is capable of receiving light in a third direction. At least one lens surface has a free-form surface shape, and has a plurality of focal points in the third direction.   The lens array according to claim 1, wherein the plurality of focal points are arranged linearly or substantially linearly in the third direction.   The lens array according to claim 1, wherein each of the lenses has the same configuration.   The lens array according to any one of claims 1 to 3, wherein the lens is formed of a photocurable resin.   The lens array according to any one of claims 1 to 4, wherein the lens is formed on a glass substrate. A head substrate having a light receiving element group obtained by grouping a plurality of light receiving elements;
A lens array having a lens facing the light receiving element group;
In the lens array, a plurality of lens rows in which the lenses are arranged in the first direction are arranged in a second direction orthogonal to or substantially orthogonal to the first direction,
The lens faces the light receiving element group in a third direction and emits light incident from the opposite side of the light receiving element group in the third direction toward the light receiving element group,
At least one lens surface of the lens has a free-form surface shape, and has a plurality of focal points in the third direction. A head substrate having a light receiving element group in which a plurality of light receiving elements are grouped; and a lens array in which a lens is arranged opposite to the light receiving element group. In the lens array, a plurality of lenses are arranged in a first direction. A plurality of lens rows arranged in a second direction orthogonal to or substantially orthogonal to the first direction;
A mounting table on which paper can be mounted;
Irradiating means for irradiating light to the mounting table,
The read head is arranged so that reflected light irradiated from the irradiation means and reflected by the paper of the mounting table, or transmitted light transmitted through the paper enters the lens from a third direction,
The light receiving element group opposes the lens on the side opposite to the incident side of the reflected light or transmitted light in the third direction, and the lens transmits the reflected light or transmitted light to the light receiving element group. Shoot towards
At least one lens surface of the lens has a free-form surface shape and has a plurality of focal points in the third direction.

Images